1. Field of the Invention
The present invention relates to a stage apparatus, which holds a reticle (original) in, for example, an exposure apparatus, an exposure method, and a device manufacturing method.
2. Description of the Related Art
An exposure apparatus for manufacturing a semiconductor device has a reticle stage and a wafer stage for aligning a reticle (mask) as an original, and a wafer as a substrate. To attain high-precision alignment in such an alignment stage apparatus, a method of providing a coarse moving stage, which moves with a large stroke, and a fine moving stage, which moves with a small stroke, to the apparatus, is disclosed in each of Japanese Patent Laid-Open No. 2000-106344, and “Ultraprecision Manufacturing Technology, Vol. 3; Technology of Measurement and Control” (first edition, Jul. 15, 1995, issued by Fuji Technosystem, pages 20-27, supervised by Akira Kobayashi).
FIGS. 8A and 8B are views showing a stage apparatus having coarse and fine moving mechanisms as described in Japanese Patent Laid-Open No. 2000-106344. A support frame (coarse moving stage) 306 connected to a feed screw system movable unit 311 for moving it with a large stroke can move on a plane guide 302. The support frame 306 has linear motor stators 305 for moving a stage (fine moving stage) 301 having linear motor movable elements 304 with a small stroke. The support frame 306 generates, together with the stage 301, a force that allows the stage 301 to move finely relative to the support frame 306.
The support frame 306 also has a pair of electromagnets 308, which sandwich the stage 301 in the Y-axis direction. Each electromagnet 308 functions as an electromagnetic coupling by generating an attraction force together with a magnetic plate 307 provided to the stage 301. As the support frame 306 accelerates/decelerates with a high acceleration/deceleration, it transmits an acceleration/deceleration force to the stage 301, using the attraction force of one of the pair of electromagnets 308.
FIGS. 3A and 3B are views showing deformation of a fine moving stage 202 upon accelerating/decelerating. FIG. 3A shows the state of the fine moving stage 202 before acceleration/deceleration. FIG. 3B shows the state in which a coarse moving stage 203 moves in the −Y direction with acceleration/deceleration to apply an acceleration/deceleration force to the fine moving stage 202 in the −Y direction. FIGS. 3A and 3B do not illustrate any electromagnets that are not involved in the force application. The fine moving stage 202 deforms to extend mainly in the Y-axis direction upon receiving the force.
FIG. 4 is a side view for explaining the section (A-A section) of FIG. 3A in the scanning direction, while the reticle holding unit 208 fixed on the fine moving stage 202 holds and aligns a reticle 201 in FIG. 3A. Deformation of the fine moving stage 202 upon accelerating/decelerating it is transmitted to the reticle 201 via the reticle holding unit 208. As deformation of the fine moving stage 202, upon accelerating/decelerating is transmitted to the reticle 201, it becomes impossible to attain high-precision alignment. Deformation of the reticle 201 makes it difficult to accurately transfer a reticle pattern drawn on it onto a silicon wafer.
In recent years, a demand has arisen for a stage apparatus that has a higher precision. For example, as shown in FIG. 3A, assume that each electromagnetic coupling transmits a force to the fine moving stage using an attraction force. When the fine moving stage is pulled by a large force from one side in one direction, it deforms, and the reticle (mask) held by the fine moving stage also deforms. These deformations pose a serious problem, especially, in a stage apparatus for an exposure apparatus, which is required to have a position reproducibility and allowable deformation amount on the order of nanometers.